Unloading mechanism for compressors



y 1936. v G. F. PFEIFER 4 UNLOADING MECHANISM FOR OOMPRESSORS Filed April 50, 1955 3 Sheets-Sheet l azye F P2 62761" ATTORNEY July 14,1936. PFE|FER 2,047,489

UNLOADING MECHANISM FOR COMPRESSORS Filed April 30, 1955 3 Sheets-Sheet 2 eazyeFPki/r ATTORNEY July' 14, 1936. ca. F. PFEIF ER 2,047,489

UNLOADING MECHANISM FOR COMPRESSORS Filed April 50, 1935 s Sheets-Sheet s cuyi V 7/ ix I BY lNvEg:

ATTORNEY y 601?? F Pfef/er Patented July 14, 1933 PATENT OFFICE UNLOADING MECHANISM FOR coMrnEssons George F. Pfeifer, Quincy, Ill., assignor to Quincy Compressor (70., a corporation of Illinois Application April 30, 1935, Serial No. 19,098

' 9 Claims. (Cl. 230-26) This invention relates to compressors and has for an object to provide fluid pressure operated means controlled by the governor to hold the compressor unloaded until the compressor reaches full speed.

A further object is to provide unloading mechanism whichwill permit of a lag or definite delay of the escape of the operating air so that the compressor is held unloaded for a short time after reaching full speed.

A further object is to provide unloading mechanism which will permit of an instantaneous action of the fluid pressure controlling valve when the pressure reaches a predetermined point at which the motor is automatically stopped to per.- mit the compressor to come to a free unloaded rolling stop.

A further object is to provide unloading mechanism which may be applied to two stage as well as single stage compressors and when usedon two stage compressors will simultaneously hold the high pressure intake valve open and at the same time vent the intercooler which connects the discharge of the low pressure cylinder to the high pressure intake, to" the atmosphere so that a one hundred per cent unloading is eifected.

A further object is to provide quick acting mechanism of this character which will be formed of a few, simple parts and which will be automatic in operation, will not require attention, and

will not easily get out of order.

With the above and other objects in view the invention consists of certain novel details of construction and combinations of parts hereinafter fully described and claimed, it being understood that various modifications may be resorted to within the scope of the appended claims without departing from the spirit or sacrificing any of the advantages of the invention.

In the accompanying drawings forming part of this specification,

Figure 1 is a fragmentary side elevation of a two stage compressor equipped with unloading mechanism constructed in accordance with the invention and shown in section.

Figure 2 is a front elevation of the parts shown inFigure 1.

Figure 3 is a longitudinal sectional view through the three-way valve.

Figure 4 is a detail sectional view showing a modified form of the invention.

Figure 5 is a detail sectional view showing a valve for causing a lag in one direction in flow through the fluid pressure pipe.

- Referring now to the drawings in. which like usual moving outwardly when the compressor is running and moving inwardly when the compressor stops.

In carrying out the invention I provide a stem l6 which is slideably fitted in a counterbore I1 formed in the end of the crank shaft and projects into a slot H3 in the crank shaft where it is connected to a bar l9 which is terminally equipped with pins that extend through the collar 2| of the governor and are terminally equipped with rounded heads 22 which are held against the governor weights by a spring 23 which surrounds the stem l6 and is confined under tension between the end wall 24 of the counterbore and a stop collar 25 carried by the stem. As the weights are thrown out by centrifugal force the stem is withdrawn by the bar is into the counterbore and as the weights move inwardly the spring I! returns the stem to initial position. The movement of the stem It by the centrifugal governor is utilized to automatically unload the cylinders every time the compressor is stopped. Unloading is accomplished by holding the intake valve of the compressor off its seat, and if the compressor is a two stage typ as illustrated, the air in both cylinders and intercooler is released to the atmosphere.

By now referring to Figure 1 it will be seen that a diaphragm 26 is mounted in a valve casing 21 which is disposed on the high pressure cylinder l3 and on one side of the diaphragm a plunger 28 is mounted in the casing and the stem 29 of the plunger is aligned axially with the high pressurelntake check valve' 30. When compressed air is admitted to the diaphragm valve casing the diaphragm will be distended and move the plunger to engage and hold open the fiitake valve 30 so that the cylinder can not pump. At the same time the air from the low pressure cylinder enters the intake port 3| of the valve casing 21 as indicated by the arrow head in Figure 1 and is vented to the atmosphere as will now be described. The stem 29 is equipped with a conical valve 32 which seats on a similar shaped seat 33 formed in an axial passage 34 in the valve casing 21. Vent openings 35 are formed in the casing above the valve 32. When air pressure is applied to the diaphragm the plunger moves downwardly as above described to open the high pressure intake valve 30 and at the same time the valve 32 will be unseated and permit the air from the low pressure cylinder, entering through the intercooler l4, topass longitudinally of the casing through ports in a bushing 36, around the valve 32, and into the atmosphere through the ports 35. In this position of the parts air is swept in and out of the high pressure cylinder through the open intake valve 32 and escapes through the openings in the bushing 36 and from thence through the ports 35 into the atmosphere. A spring 31 surrounds the stem of the plunger and is seated in a. housing 38 carried by the bushing 36. The spring closes the conical plunger valve 32 and returns the plunger to initial position when air pressure is removed from the diaphragm, the plunger stem at the same time moving away from the high pressure intake valve to permit the valve to function.

Compressed air is supplied to the diaphragm valve casing on one side of the diaphragm through a pipe 39 which is connected to a threeway valve casing 49, compressed air being sup plied to the valve casing through a pipe 4| which is connected to the compressed air receiver or tank not shown. The three-way valve housing is substantially cruciform in contour as best shown in Figure 3, two of the aligned branches 42 and 43, being connected to the pipes 39 and 4| by screw threaded connectors 44 and 45, and the other two branches having seated therein valves 46 and 41 which are disposed in alignment with the above described stem |6 of the centrifugal governor. The valve 46 is faced with packing material 48 so as to seat tightly against a seat 49 and seal an axial duct 50 when the valve is closed. A threaded cap 5| is screwed on to the valve housing to house the valve and the cap is provided in the end wall with a vent opening 52 through which air is released from the diaphragm valve above described as will presently be explained.

The valve 41 is likewise faced with packing material 53 to fit tightly against a seat 54 formed at the opposite end of the axial duct 56. A spring 55 is housed in a threaded plug 56 screwed into the valve housing and exerts pressure against the valve 41 to normally hold the valve closed.

A duct 51 is formed in the housing at a right angle to the axial duct 50 and connects the axial duct with the pipe 39. A duct 59 is formed in the housing and connects the pressure supply pipe 4| with a chamber 59 which houses the valve 53. The stems of both valves 46 and 41 are provided with frusto-conical tips 66 which abut eachother at the duct 51.

By now referring to Figure 1 it will be seen that when the compressor is stopped the governor weights are disposed inwardly and thespring 23 forces the governor stem 6 against the valve 46 holding the valve closed and simultaneously holding the valve 41 open so that. the air pressure from the pipe 4| passes through the duct 58, chamber 59, duct 59, duct 51 and pipe 39 to distend the diaphragm and hold the conical valve 32 open and the high pressure intake valve 39 unseated. In this position of the parts the cylinders are unloaded. When the compressor is started the unloaded condition is maintained suificiently long to permit the motor and the compressor to come to full speed and when full speed is reached the governor weights 5 have moved outwardly and withdrawn the stem l6 from contact with the valve 46 so that the spring 55 acts on the valve 41 to close this valve and shut ofi the air supply to the diaphragm chamber through the port 58 and at the same time will open the valve 46 to unseal the axial port 59 and permit air entrapped in the pipe 39 and diaphragm valve casing to bleed through the duct 51, axial duct 50 and port 52 into the crank case of the compressor as best shown in Figure 1.

It does not require a long time for the governor weights to reach extreme outer position and to prevent the load coming on the motor too suddenly, the stem 6| of the valve 46 is a close fit and thereby restricts the flow of air from the diaphragm valve assembly, thereby holding the compressor unloaded for a short time even after the motor has come to full speed. The stem 62 of the valve 41 is provided with a fiat side 63 which permits quick passage of the air through the duct 51 into the pipe 39 to promote rapid action when stopping. In practice, the governor weights move inwardly after a speed of 300 R. P. M. is reached, thereby permitting the compressor to come to a rolling stop. During the period from 300 R. P. M. to a complete stop, the low pressure piston is doing compression work, but this air is expelled through the intercooler l4 and out through the ports 3 |,-36 and 35 in the diaphragm valve assembly.

While the valve stems 6| and 63 respectively prevent the load coming on too suddenly, and promote rapid unloading when stopping, the same purpose may be accomplished by the check valve mechanism shown in Figure 5 which may be connected to the pipe 39 to give free flow in one direction and restricted flow in the opposite direction. In this modification the valve casing 65 is provided with an axial passage 66 of rather large diameter in which is mounted a check valve 61 which closes toward the three-way valve 40 and seats on a tapered seat 68, the valve being provided with wings 69 below the seat which form a bearing for the valve. A spring 10 is confined in a recess 1| formed in a cap nut 12 which is threaded into one end of the casing 65, the spring exerting pressure upon the valve 68 to normally hold the valve seated. Air let into the pipe 39 by the three-way valve to the diaphragm valve assembly will unseat the valve 61 and pass quickly to actuate the diaphragm valve.

A by-pass 13 is formed in the casing 65 to connect the ends of the passage 66 around the check valve 61, and a needle valve 14 is threaded into the side of the casing and enters the by-pass. Venting of the air from the pipe 39 through the by-pass 13 around the closed check valve 61 is thus restricted to hold the compressor unloaded for a short time after the motor has come to full speed. The axial passage 66, when the check valve 61 is opened, gives rapid action when stopvalve assembly 11 which communicates direct 70 with the bore of the high compression cylinder through a lateral duct 18. The check valve assembly comprises a cruciform casing 18 which is provided in the lateral branches with air vents 19 that communicate with an axial passage 76 aoaaaee $3 in the aligned branches. A valve 88 is housed in a valve casing 82 which is threaded on to the outer branch of the cruciform casing and is provided with a packing member 83 which engages with the valve seat 8d and forms a tight fit. E'he valve is provided with a stem 85 which is slidably fitted in the axial passage ti] and is equipped with a frusto-conical valve ht which opens toward the cylinder and seats on a conical seat ill as shown. A spring 88 surrounds the valve stem and holds the conical valve normally closed and the valve 85 normally open.

Air let into the pipe 16 by the three-way valve will act against the valve 80 and close the valve, at the same time opening the valve tti whereby the high pressure cylinder 89 will be vented to the atmosphere through the passage it, around the valve 8%, and through the vent ports iii, thus unloading. the compressor. When the air is shut off by the three-way valve from the pipe it the spring 38 will close the conical valve 85 and open the valve ti which is the position of the parts when the compressor is pumping.

From the above description it is thought that the construction and operation of my invention will be fully understood without further explanation.

What is claimed is:

l. Ina two stage compressor, high and low pressure cylinders, an intercooler connecting the discharge port of the low pressure cylinder with the intake port of the high pressure cylinder, a diaphragm valve adapted to simultaneously hold the high pressure cylinder intake valve unseated and vent the low pressure cylinder and the intercooler to the atmosphere, a governor, and means controlled by the governor for admitting a fluid pressure medium to operate the diaphragm valve.

2. An unloading device for compressors comprising a cylinder, a governor having a stem moved axially by opening and closing of the governor weights, a diaphragm valve in the cyl inder for venting the cylinder to the atmosphere, a pipe for supplying a fluid pressure medium to the diaphragm valve to hold the valve open, a three-way valve casing in the pipe, and aligned valves in the casing spring pressed in one direction to vent the pipe and moved in the opposite direction by the governor stem to hold pressure in said pipe and actuate the diaphragm valve.

3. An unloading device for compressors including a cylinder, a governor, a diaphragm valve adapted to simultaneously unseat the cylinder intake valve and vent the cylinder to the atmosphere, a fluid pressure pipe for conducting a fluid pressure medium to the diaphragm valve, 2. threeway valve in the pipe controlled by the governor to admit a fluid pressure medium to the dia phragm valve to actuate the valve, and a spring controlling the three-way valve to vent the fluid pressure medium from said pipe.

4. The combination with a compressor, of a governor, a diaphragm valve controlling the intake of the compressor to load and unload the compressor, a three-way valvecontrolled by the sure medium in one direction to delay loading the compressor.

5. The combination with a compressor, of a governor, a diaphragm .valve controlling the intake of the compressor to load and unload the it compressor, and a three-way valve assembly having aligned valves controlled by the governor to alternately supply and release a fluid pressure medium from the diaphragm valve for opening and closing the diaphragm valve, one of the 15 ahgned valves restricting the flow of the fluid pressure medium. from the diaphragm valve to delay loading the compressor until a predetermined speed has been reached.

6. The combination with a compressor, of a governor, a diaphragm valve controlling the intake of the compressor to load and unload the compressor, a three-way valve assembly having aligned valves controlled by the governor to alternately supply and release a fluid pressure me 25 drum from the diaphragm valve for opening and closing the diaphragm valve, one of the aligned valves having a flat side for accelerating flow of the fluid pressure medium to the diaphragm valve to hasten action of the diaphragm valve in unloading the compresspr.

7. The combination with a compressor, of a governor, a diaphragm valve controlling the intake of the compressor to load and unload the compressor, a'three-way valve controlled by the 35 governor to alternately supply a fluid pressure medium to the diaphragm valve for opening the valve and to release the fluid pressure medium from the diaphragm for closing the valve, and

a check valveassociated with the three-way 40 valve having a by-pass restricting release of the fluid pressure medium from the diaphragm valve.

8. The combination with a compressor, of a governor, a three-way valve controlled by the governor, a check valve assembly for venting the compressor cylinder to the atmosphere, and a pipe connecting the three-way valve with the check valve assembly, said three-way valve being adapted to alternately supply a fluid pressure medium through the pipe to open the check valve and to release the fluid pressure medium from the pipe to close the check valve.

9. The combination with a compressor, of a centrifugal governor, a stem moved by the governor weights, a three-way valve casing, aligned valves in the casing moved in one direction by the governor stem and spring pressed in the opposite direction when the governor stem recedes, a valve assembly adapted to vent the compressor cylinder to the atmosphere, a pipe for to supplying a fluid pressure medium to the threeway valve casing, and a pipe connecting the three-way valve casing with said valve assembly for supplying and releasing the fluid pressure medium from the valve assembly. 5

GEORGE F. PFEIFER. 

